Arm positioned type head



March 7, 1967 FRA K ET AL 3,307,677

ARM POSITIONED TYPE HEAD Filed 001;. 6, 1965 INVENTORS.

EDGAR H. FRANK EDWIN L. LIBBY THOMAS N. WATKINS ATTORNEY.

United States Patent 3,307,677 ARM POSITIONED TYPE HEAD Edgar H. Frank, Edwin L. Libby, and Thomas N. Watkins, Lexington, Ky., assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Oct. 6, 1965, Ser. No. 493,399 Claims. (Cl. 197-52) This invention relates to printing mechanisms, and more particularly to a printing head carrying a group of image forms having improved means for removably attaching the printing head to a drive member.

In Patent No. 2,895,584 to J. E. Hickerson et al. there is shown a print head having characters formed on its surface to effect printing when engaged with a platen. The head is in the form of a truncated sphere and has the characters arranged in rows and columns on the spherical portion of its surface. By rotating the head on a supporting block while the latter is tilted about a horizontal axis, any one of the characters may be moved to a printing position.

In Patent No. 3,001,628 to R. W. Rice, Jr. a spring and cap mechanism is shown to hold the type head on the block by means which may be easily released to permit replacement of the head by another bearing a different style or arrangement of characters. Handles of the spring element shown in Patent 3,001,628 are gripped and the arm portions of the spring are forced apart by a squeezing pressure, usually applied with two fingers of one hand. With the spring arms thus sufiiciently spread, the element can be lifted from or placed upon the drive member of the printer as desired. Removal of the squeezing pressure when the type head is properly located on the drive member allows the spring to close into a holding position with a groove on the drive member.

It is an object of this invention to provide a removable printing element usable interchangeably with the device taught in Patent No. 3,001,628; but improved in the respects noted below.

Some difficulty in utilization is experienced with the prior device because of the significant spring force which must be overcome by the finger grip of the individuals using the prior device. This return spring force, as such, is only a minor irritation since it is not great enough to cause significant fatigue. However, slight relaxations or relocations of the fingers holding the spring handles can result in the spring forcing itself free. The only'clean area to grip in the prior device is at the spring handles, since the remainder of the type element is either dirtied by contact with the typewriter ribbon or is. not conformed to aid a person in holding the element. Thus, when the spring forces itself free, it often happens that the only grip is lost and that the prior device is therefore dropped. Dropping the device is at least a substantial irritation, and frequently the type head is broken and destroyed by the impact of a fall.

It will be appreciated, of course, that mechanical requirements dictate that the head be as light weight and low in angular inertia as possible. This dictates that no grip can be added to the element which would also add significantly to weight and angular inertia. The prior art device, which provided only the spring handles as a grip, was therefore a reasonable design.

It is a further object of this invention to create a suitable type head which is easily and surely handled.

It .is a more specific object of this invention to create a suitable type head which can be handled with reduced possibility of breaking the type head and also with maximum convenience in handling and in avoiding inky areas on the type head.

In accordance with this invention an arm is provided which is linked to cams to force apart the arms of the holding member or spring. Any spring forces are reduced by the leverages provided.

Further in accordance with this invention a latch is provided on the arm. The latch coacts with means on the type head so that when a spring is spread apart the return forces can be neutralized indefinitely by the latch.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

FIG. 1 is a top view of the type head assembly in accordance with the preferred embodiment of this invention.

FIG. 2 is a bottom View of the cap in accordance with the preferred embodiment of this invention.

FIG. 3 is a detail of the handle or arm.

FIG. 4 is a detail of the cam shaft in accordance with the preferred embodiment of this invention.

FIG. 5 illustrates the spring of the preferred embodiment of this invention.

FIG. 6 is a section view through 66 of FIG. 1, but showing the handle latched open.

The assembly As shown in FIG. 1, a print head 1 in the form of a light weight, hollow, truncated shell has characters 3 on its surface for engagement with a platen, not shown, to effect printing. The lower end of the head is open to receive driving mechanism extended into its interior and to permit a tilting of the head about its center. The print head 1 is substantially identical in structure and function to that described in Patent 3,001,628, with the addition that diametrically opposite the notch (15 in the patent) on the sleeve (4 in the patent) a keyway is fashioned up the length of the sleeve. This keyway meshes with a spline on the drive member (5 in the patent) to further insure proper location of the head 1 with regard to the rotate-tilt mechanisms of the printer.

In accordance with this invention the head 1 carries a cap 5, in which a spring 7 is looped around two symmetrically separated studs 9', 9" depending from the inside of the top of cap 5. In a manner quite similar to the prior device, cap 5 carries stud portions 11', 11", 11" which are reduced in cross section at their lower ends to extend through openings in the upper surface of head 1. After the cap 5 has been mounted on the head 1 with the stud portions extending through the openings, a heat instrument is applied to the lower ends of the stud portions 11 for softening and deforming them so as to secure the cap firmly on the head. The inside of the cap is recessed to provide between cap 5 and head 1 a chamber into which the upper end of the drive member of the printer projects in the manner of the prior device.

The cap 5 has a T-shaped, handle and cam slot 13 (best seen in FIG. 2) occupying most of one diameter. The cap has a small detent slot 15 situated parallel with and approximately inch behind the cross of T slot 13. The entire cap 5 is made in one piece of a tough, resilient plastic, preferably of one of the polyacetals, and is approximately inch thick. (Delrin-A product of E. I. du Pont de Nemours and Co. is specifically preferred for use as the plastic material.)

At the two ends of the cross of T-shaped slot 13 are portions of increased plastic body which are formed around slots .17 and .17", and slots 17' and 17" are suitable to receive and journal the shafts 18' and 18" of cam shaft 19 (see FIG. 4). Cam shaft 19 normally rests by gravity on the top of head 1 and is journalled and held in the other directions by slots 17' and 17".

Handle 21, carrying latching detent 23 (FIG. 3), is

formed around shaft 19 and extends more than the length of the long slot of T-shaped slot 13. When in the down position, handle 21 meshes with slot 13 so as to combine with cap 5 to form a smooth surface on the top of cap 5. Extensions 25' and 25" on handle 21 at a location away from cam shaft 19 are positioned on each side of handle 21 so as to mesh with bevelled areas 27' and 27" of cap 5 at complementary locations along slot 13. The extensions 25 push aside and then snap under bevelled portions 27 and 27" to thereby latch handle 21 down during the normal rotate, tilt, and print movements of the printer.

The handle 21 extends over an indented bay 27 in cap 5. The bay 27 is provided to leave room for the finger of a person grasping the end of handle 21.

Before describing the operation of the unit, the structures and functions involved will be described in somewhat more detail.

The cap FIG. 2 is a bottom view of the cap 5, while FIG. 1, of course, shows a top view of the cap as it is connected into the assembly. The studs 11, 11", and 11" will extend into the head 1 in the manner of the prior art device to permanently connect cap 5 to head 1. As illustrated in FIG. 2, T-shaped slot 13 is merely an extended opening in the unitary plastic cap 5.

Studs 9 and 9" will position spring 7 by extending through the two loops formed in spring '7 (FIG. 5). Slot 15 is operative to weaken the top edge 29 of T-shaped slot 13. As will be explained, this weakening is necessary to permit edge 29 to latch over detent 23 without undue stress required in the system.

The slots 17' and 17 are clearly shown in FIG. 2. These slots 17 receive the shafts 18 and 18 of cam shaft "19. The plastic between each slot 17' and 17" and the nearest part of the circumference of cap 5 is built up to about 0.06 inch thickness to thereby provide added structural stability since the entire print element often will be held by handle 21 and the forces will therefore be transferred to slots 17' and 17'.

The handle FIG. 3 illustrates the handle 21 alone. The latching detent 23 is a small nub extending from the handle about 0.02 inch and formed as an integral part of the arm or handle 21 across the entire width of handle 21. Latching detent 23 coacts with the top edge 29 of slot 13 as will be described. The entire handle, including detent 23, is molded as a single piece of plastic, preferably of the same polyacetal resin from which cap 5 is fashioned.

The small extensions 25' and 25 on handle 21 are most clearly shown in FIG. 3. They shove aside cap 5 at bevelled portions 27' and 27", after which the inherent resilience of bevelled portions 27 causes them to snap back over extensions 25 and hold the handle firmly to cap 5. The handle 21 is freed by a slight but significant rotating pressure on the handle 2 which forces the bevelled portions 27 aside, freeing extensions 25 and therefore freeing handle 21.

The spring Spring 7 is shown in FIG. 5 in its relaxed position and in a bottom view (assuming FIG. 1 is a top view). It is a single element of 0.04 inch diameter music wire steel, surface treated with nickel and having a heavy squeeze force in proportion to the dimensions of the spring. The wire is twisted to form the two loops and the two symmetrically extending arms shown. The natural resilience of the spring material causes the arms to firmly close toward each other (FIG. 1 shows the arms properly gripping shaft [shaft 35 shown in FIG. 6]).

The cam shaft The cam shaft (FIG. 4) is a machine steel part in which a hole is drilled laterally and a single, small steel bar is inserted to form shafts 18' and 18". The two d faces 31 and 31" of shaft 19 are machined to form smooth surfaces each having an angle of about 45 to a perpendicular to the long axis of cam 19. It is case hardened (5560 on the Rockwell C scale) to resist being gouged by spring 7 during use. The cam shaft has longitudinally extending diamond knurls at center portion 33, which is also recessed. Handle 21 is wrapped entirely around center portion 33 in an injection molding process which forms the entire handle 21, and a study bond is thus formed by the interlocking with the knurls. The recess of center portion 33 is dimensioned to just fit the wrapped around portion of handle 21 so that the wrapped around portion of handle 21 does not bulge beyond the adjoining surfaces of shaft 19.

Operation In operation, the entire print head element is in the rest position on the printer when it is located as shown in FIG. 1. Handle 21 points along the perpendicular to the direction in which print movement toward the paper in the machine occurs. With the handle 21 in this position movement force on the handle does not coincide with the movements permitted by the printer. The handle 21 therefore can be moved up and down with relative ease. With handle 21 down as shown in FIG. 1 the cam faces 31' and 31 are rotated to allow spring 7 to close around the groove at the top of shaft 35 (FIG. 6). The spring thus holds the element against vertical movement with relation to shaft 35. Rotating, tilting, and printing may be conducted as desired. Detents 25 and 25 are latched under cap 5 to thereby hold handle 21 in place.

To remove the type head (for any purpose, generally to exchange it with another type head carrying characters of different style) a thumb or finger is inserted in bay 27 so as to be under the end of handle 21. Handle 21 is then manually forced upward about to the position shown in FIG. 6. A moving force as just described on handle 21 causes cap 5 to easily yield so that detents 25 and 25" are freed.

The handle movement pivots cam 19 an equal amount. Cam surfaces 31 and 31 are eccentric with regard to the arms and therefore force the arms of spring 7 apart to free spring 7 from the groove at the top of shaft 35. With the spring '7 thus open, the type head can be lifted from the printer at this time. However, it is preferred that handle 21 be pivoted until detent 23 on handle 21 contacts and forces aside edge Zfi of slot 13. Slot 15 weakens edge 219 to permit edge 29 to yield sufficiently. The natural resilience of the plastic used causes edge 29 to snap back over detent 23- and to thereby lock handle 21 in the up posture shown in FIG. 6. The forces of spring 7 are completely neutralized, as they are reduced by the directions of force on camming surfaces 31 and 31 and the reduced forces are fully resisted by the latch between detent 23 and edge 29. The element may be carried bodily by simply grasping the handle 21.

To insert the same or a new element on to the printer, a print element with the handle extended up and latched may be grasped by the handle. It is centered over shaft 35, and properly located to accommodate the notchin g members between shaft 35 and head 1. The element is lowered into position and the handle is then gently pushed down into the position shown in FIG. 1.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A single element print head comprising, in combination:

a truncated spherical shell,

characters formed on the spherical portion of said shell,

a handle member, a cap mounted on one end of said shell, said cap holding said handle member for limited movement, an element having thin arms adapted to move between open and closed positions, movable means pivotable about an axis and having at least one face surface inclined at an acute angle to said axis, said movable means being linked to said handle for movement with said handle and being linked through said face surface to said element having arms for controlling said open and closed positions of said element having arms. 2. The print head as in claim 1 wherein said element having arms is a spring.

3. The print head as in claim 2 wherein said handle carries means to latch said handle to said cap in a position to hold open said spring.

4. The print head as in claim 2 wherein said spring is aside to thereby latch said handle and wherein the material of said cap behind said edge is at least partially removed so as to permit said edge to move aside and move back over said detent and wherein said edge moves back by inherent resilience of the material forming the said edge of said cap.

7. The print head as in claim 1 wherein said handle carries means to latch said handle to said cap in a position to hold open said element having arms.

8. The print head as in claim 7 wherein said means to latch is a detent on said handle positioned to force an edge of said cap aside, and said edge of said cap is so fashioned as to move back over said detent after being forced aside to effect latching.

9. The print head as in claim 7 wherein the material of said cap behind said edge is at least partially removed so as to permit said edge to move aside and wherein said edge moves back by inherent resilience of the material forming the said edge of said cap.

10. The print head as in claim 9 wherein said handle carries at least one extension to force aside and latch under said cap to hold said handle in position when said element having arms is in the closed position.

References Cited by the Examiner UNITED STATES PATENTS 2,969,864 1/1961 Holgate 197-52 3,001,628 9/1961 Rioe 197-52 3,027,988 4/ 1962 Tackett 197-52 ROBERT E. PULFREY, Primary Examiner. E. S. BURR, Assistant Examiner. 

1. A SINGLE ELEMENT PRINT HEAD COMPRISING, IN COMBINATION: A TRUNCATED SPHERICAL SHELL, CHARACTERS FORMED ON THE SPHERICAL PORTION OF SAID SHELL, A HANDLE MEMBER, A CAP MOUNTED ON ONE END OF SAID SHELL, SAID CAP HOLDING SAID HANDLE MEMBER FOR LIMITED MOVEMENT, AN ELEMENT HAVING THIN ARMS ADAPTED TO MOVE BETWEEN OPEN AND CLOSED POSITIONS, MOVABLE MEANS PIVOTABLE ABOUT AN AXIS AND HAVING AT LEAST ONE FACE SURFACE INCLINED AT AN ACUTE ANGLE TO SAID AXIS, SAID MOVABLE MEANS BEING LINKED TO SAID HANDLE FOR MOVEMENT WITH SAID HANDLE AND BEING LINKED THROUGH SAID FACE SURFACE TO SAID ELEMENT HAVING ARMS FOR CONTROLLING SAID OPEN AND CLOSED POSITIONS OF SAID ELEMENT HAVING ARMS. 